I just put a used Throttlemeister on and it is a bit hard to engage. I got no instructions. So far the easiest for me is to just reach over with the other hand and engage it. I read a suggestion of rolling it on with the same hand but not much luck doing that. What do you all do?

When properly installed it should be easy to engage. Even when fully locked you should be able to move the throttle. I have mine adjusted so that I can lightly engage it to relieve my grip but still make minor changes to speed. The number and thickness of the shims (washers) is how you adjust it. It should never lock so tight that you can't move the throttle in an emergency.

I just put a used Throttlemeister on and it is a bit hard to engage. I got no instructions. So far the easiest for me is to just reach over with the other hand and engage it. I read a suggestion of rolling it on with the same hand but not much luck doing that. What do you all do?

So far I like the look and build. I have never had the other one.

That seems like a difficult way to engage the TM. When I want to lock the throttle, I use my thumb and index finger to control the throttle, and turn the TM bar end counterclockwise with my little finger and ring finger. This locks the throttle, then you can make a final adjustment with your full hand to set the speed after it is locked.